CYCS and idiopathic pulmonary fibrosis: In this work, we demonstrated that IPF fibroblasts presented a marked decrease in basal cytochrome c levels and its release after stimulation with mitomycin C. Cytochrome c is a crucial signaling molecule during apoptosis, but it also plays an essential role in oxidative phosphorylation by transferring electrons from complex III to complex IV of the electron transport chain [29].